[Bug 263062] tcp_inpcb leaking in VM environment

From: <bugzilla-noreply_at_freebsd.org>
Date: Wed, 30 Aug 2023 09:39:45 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=263062

paul vixie <paul@redbarn.org> changed:

           What    |Removed                     |Added
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                 CC|                            |paul@redbarn.org

--- Comment #14 from paul vixie <paul@redbarn.org> ---
> ...
> For now the server already has stopped working three times with:
> Aug 10 07:25:38 mailrelay kernel: [zone: udp_inpcb] kern.ipc.maxsockets limit
> reached
> 
> I guess the DNS queries are the reason for this.
> ...

this is normal for all recursive dns servers not just unbound, because kaminsky
resistance requires randomized source udp port numbers for cache miss
transactions, which in turn requires a moderately large working set of bound
udp sockets, with heavy churn.

if this turns out to be chipset dependent, we should be looking at atomic test
and set operations. i long ago turned off hyperthreading because
microarchtectural details turned out to be motherboard dependent. there may be
similar problems still lurking, but on a lark, maybe try turning off
hyperthreading?

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